Adjustable high-frequency inductance



Patented May 21, 1946 ADJUSTABLE HIGH-FREQUENCY IN DUCTAN CE Frank Verity, Jr., Oyster Bay, N. Y., assignor to Press Wireless, Inc., New York, N. Y., a corporation of Delaware Application January 6, 1945, Serial No. 571,634

1 Claim.

This invention relates to inductance coils and more particularly to tuning inductances for use in high powered equipment.

A principal object of the invention is to provide an improved manner of short-circuiting one or more turns of a rigid inductance coil.

A feature of the invention relates to a high frequency tank inductance of the type having rigid self-supporting turns with special contact lugs integrally attached thereto and arranged to receive the sections of a special short-circuiting bar.

Other features and advantages not specifically enumerated will be apparent after a consideration of the following detailed descriptions and the appended claim.

In the drawing,

Fig. 1 is a front view of the inductance and short-circuiting bar according to the invention.

Fig. 2 is a sectional view of Fig. 1 taken along the line 2-2 thereof.

Referring to the drawing, there is shown an inductance coil I which is formed of rigid metal stock preferably, although not necessarily, of hollow metal'tubing. When the inductance is to be used as a water-cooled inductance, the ends 2 and 3 are connected to a suitable water supply in the well-known manner. Preferably, the coil is formed of copper or other low resistance metal or alloy. the exterior surface of which is heavily silver-plated to reduce contact resistance to a minimum. Each turn of the coil has integrally attached thereto a flat contact lug 4 having a slot 5 therein. The lugs 4 are all arranged so that their slots 5 are in alignment longitudinally of the coil.

When it is required to change the effective inductance, one or more turns thereof are shortcircuited by means of the short-circuiting unit 5. This short-circuiting unit consists of a central bar 8 of low resistance metal or alloy such for example as "Tobln bronze, the length of which is correlated with the number of turns of the coil I to be short-circuited. The diameter of the rod 8 is slightly smaller than the width of the slots 5 in the various lugs 4. The lefthand end of rod 6 has rigidly fastened thereto as by pinning, a knurled knob I. The rod 5 is threaded either throughout its entire length, or for a considerable length adjacent its right-hand end. The rod 6 is adapted to receive in a freely slidable manner a series of brass collars 8, the ends of which are preferably, although not necessarily, tapered as indicated by the numeral 9 and the extreme end of which are flat so as to make a fiat surface contact with the respective lugs 4. The number of collars 8 which are placed on the rod 6 is determined by the number of turns of the coil I to be short-circuited, the length of each collar 8 being the same as the distance between adjacent faces of successive lugs 4.

For the purpose of clamping the several collars in rigid contact between the respective lugs, a brass. nut I0 is threaded on to the end of rod 6 and a take-up washer I I may be interposed between this nut and the first lug 4. While the drawing shows a bar for short-circuiting four.

successive turns of the coil I, it will be understood that a greater or less number of turns may be short-circuited by using a longer or shorter bar 6 with a corresponding greater or less number of collars 8 thereon.

If the coil I is of the balanced push-pull type where it is necessary to short-circuit an equal number of turns on each half of the coil, separate short-circuiting bars and sleeves may be used for the respective halves of the coil. For example, if each half of the inductance coil has eight turns, it may be requiredto use shortcircuiting bars to short-circuit 14 turns, 12 turns, 10 turns, 8 turns, etc. In that case, each shortcircuiting bar may be of exactly the same type, the length and number of collars varying according to the number of turns to be shortcircuited. In the case of single-ended coils such as shown in Fig. l,'it may be convenient to use one standard length of short-circuiting bar for short-circuiting' different numbers of turns. For example, a bar normally designed to short-circuit a maximum of 10 turns may be used for shortcircuiting as few as 5 turns, it being necessary merely ,to take up on the nut III or the nut I to the extent necessary to make rigid connections between the coil lugs and the respective collars 8.

While certain specific embodiments have been disclosed herein, it will be understood that various changes and modifications may be made without departing from the spirit and scope of the invention.

What is claimed is:

An adjustable inductance comprising a plurality of rigid helical coil turns, each turn having an integral slotted lug with the slots in successive turns in longitudinal alignment, and shortcircuiting means for certain of said turns and comprising a bar having a series of metal sleeves slidably mounted thereon, and means to clamp each sleeve between adjacent pairs of said lugs.

FRANK VERITY, JR. 

